This invention relates to an electronic circuit for use with an electrical generator having a voltage regulator which responds to raise or lower control signals to change the generator output voltage to approach the voltage of a bus to which the generator is to be connected.
When an electrical generator is to be connected to an energized electrical system, the generator voltage, frequency and phase angle must be matched to the those of the electrical system. While electrical apparatus is presently available which will accomplish this matching prior to closing the generator breaker the time required to match the generator voltage to the electrical system voltage (i.e., bus voltage) is very often excessive.
For example, some presently available circuits will provide a continuous raise or lower signal until the difference between the generator voltage and bus voltage is adjusted to within permissible limits. If a continuous raise signal was being applied (i.e., the generator voltage was too low), the generator voltage may overshoot the desired value and hunt for some time before a voltage match is attained.
Some voltage matching systems have attempted to solve this overshooting and hunting problem by periodically providing raise or lower control signals which are pulses having a varying duration. For example, the pulses will have a settable pulse width or duration produced when the voltage difference is above a predetermined magnitude (e.g., 20 volts). When the voltage difference is below this predetermined magnitude, the pulse width will linearly decrease until the voltage difference reaches another predetermined magnitude (e.g., one volt) below which magnitude pulses will no longer be provided. Thus, below this latter predetermined magnitude, the generator voltage is not controlled and may not reach an acceptable level. The generator voltage disadvantageously will not be "fine tuned" and thus one may not attain the desired close match between the generator and bus voltage.